Carburator Orfice Plug Replacement

[svenr]

When is it necessary to replace carburator orfice plugs? My service manual lists 50 different orfice plug sizes anywhere from 0.014 to 0.073 in size.

The manual states "it is occasionally necessary to replace carburator orfices to improve engine running characteristics". Has anyone replaced the stock orfice, and if so, when would it be necessary?

Engine is 1992 - Johnson 9.9 hp Long shaft. I operate the boat generally between sea level and 2000 ft elevation.

 

[rickdb1boat]

Re: Carburator Orfice Plug Replacement

Higher elevations would be the main reason. I don't know that 2000' would be significant enough to warrant a change. What problems are you having now and are they elevation related?

 

[jimmbo]

Re: Carburator Orfice Plug Replacement

2000 ft is not considered High altitude. 3500+ perhaps. Since 2 stroke engines with fixed carbs are jetted slightly rich, leaning out will increase your power. However that old adage ' two stroke engines make their most power immediately before they blow up' is more likely to prove itself correct.

If it is not broke, don't mess with it.

 

[svenr]

Re: Carburator Orfice Plug Replacement

I don't know if my problem is elevation related, but I would guess not. Here is the problem I am currently having.

http://forums.iboats.com/showthread.php?t=192529

Based on a few previous threads, I am thinking the motor *may* be running a little rich. Not sure if leaning out the mixture would help, but I am pretty sure it is carb / fuel / or iginition related. Sorry I can't narrow it down more. =)

 

[F_R]

Re: Carburator Orfice Plug Replacement

I would be VERY surprised if the carb orfice has anything to do with your hard starting problem. Even if you deliberatly flooded it out with the choke, it should restart with a few pulls.

It takes more voltage to fire a warm spark plug than it does a cold one. Therefor, I would say your problem is igniton related. Something is failing as it warms up.

 

[svenr]

Re: Carburator Orfice Plug Replacement

How should I test for an iginition related problem? Or rather, what is the easiest way to check? The service manual section on the ignition is pretty complex. I'm not sure where to start.

 

[BoatBuoy]

Re: Carburator Orfice Plug Replacement

Whenever it won't start, pull the plugs and see if their fuel-soaked.